The present invention pertains to a method of manufacturing threaded nuts and to threaded nut articles produced by such method.
Threaded nuts are in widespread use throughout the world in virtually every field of technology and numerous techniques have been devised to produce such nuts in commercial quantities and in the various standard thread sizes. The traditional method of forming threaded nuts comprises forming on a nut forging machine nut blanks having the desired geometrical profile, such as hexagonal, square, etc., and then tapping the nut blanks to form the screw threads thereby producing threaded nuts. This technique is disadvantageous in that the material removed from the nut blanks during the tapping operation is wasted and such results in considerable material waste, especially during formation of large nuts. This prior art technique is also unsuitable for mass production due to the gradual wearing away of the screw taps which eventually results in unacceptable thread pitch tolerances. Another disadvantage is that a considerable monetary investment must be made to obtain a full set of screw taps corresponding to all of the standard thread sizes currently in use, and as the screw taps become worn through repeated use, they must be replaced and this necessitates further expense.
In order to overcome the foregoing disadvantages associated with the screw-tapping technique, it has been proposed to eliminate the tapping operation by forming the nut threads of a coil spring insert which is inserted into a preformed hollow nut casing. The interior helical edge of the coil spring insert defines the screw thread so no screw-tapping operation is necessary. However, manufacturing difficulties have been encountered in this technique and it is not heretofore been possible to satisfactorily produce threaded nuts on a commercial scale. One major difficulty resides in the manner of affixing the coil spring insert to the nut casing and the current means employed for this purpose tend to be time-consuming and somewhat intricate and hence unsuitable for mass production. For example, one proposal known in the art is to provide inturned lips on the nut casing so as to retain the coil spring insert in place, however this creates problems in forming the lips and in rigidly securing the coil spring insert to the nut casing so as to preclude relative rotation between the two. A further drawback of the currently used coil spring insert techniques is that they require some finishing operation due to the manner in which the coil spring insert is bonded to the nut casing.